(a) Field of the Invention
The present invention relates to a method and a system that learns an operation of an engine clutch using a hydraulic pressure sensor and a motor of a hybrid vehicle.
(b) Description of the Related Art
In general, a hybrid vehicle may reduce exhaust gas and improve fuel efficiency by using a motor as a power source, as well as an engine. In the hybrid vehicle, as illustrated in FIG. 1, an engine 11, a motor 12 and a transmission 13 may be arranged in series. It should be noted, however, that hybrid vehicles may be arranged in many different configurations, including in parallel, in which case the engine and the motor are engaged and disengaged from the transmission accordingly.
In the hybrid vehicle 10, an engine clutch 14 that transmits driving power and blocks transmission of the driving power may be disposed between the engine 11 and the motor 12. FIG. 2 is a conceptual diagram of the engine clutch 14. As illustrated in FIG. 2, the engine clutch 14 may include a friction material PE (polyethylene) moving via pressure (e.g., hydraulic pressure) from a fluid (e.g., oil) FL of which quantity is controlled by operation of a solenoid valve SOL and a return spring SP to restore the friction material PE to an original state when operation hydraulic pressure is released from the friction material PE. The solenoid valve SOL is generally controlled by a current. Hydraulic pressure applied to engine clutch 14 from the solenoid valve SOL may be measured with a hydraulic pressure sensor. For example, the hydraulic pressure sensor may be a hydraulic pressure sensor applied to a DCT (dual clutch transmission).
The solenoid valve SOL is operated to allow the hydraulic pressure applied to the friction material PE to increase as current applied to the solenoid valve SOL increases. When the hydraulic pressure applied to the friction material PE increases, contact frictional force of the friction material PE increases. Accordingly, as illustrated in FIG. 3, torque transmitted by the engine clutch 14 is increased in proportion to the current applied to the solenoid valve SOL.
In the hybrid vehicle 10, an integrated starter generator (ISG) 15 that operates the engine 11 or operates as a generator may be mounted to the engine 11. The ISG 15 may be called a hybrid starter generator (HSG) in vehicle manufacturing.
The hybrid vehicle 10 may run in an electric vehicle (EV) mode that utilizes power from the motor 12 to provide a driving force to the transmission and output shaft. Further, the hybrid vehicle 10 may also run in a hybrid vehicle (HEV) mode using torque from the engine 11 as main power and torque from the motor 12 as auxiliary power. Further, the hybrid vehicle 10 may run in a regenerative braking (RB) mode in which braking and inertia energy of the hybrid vehicle is collected through power generated by the motor and the battery is charged when the hybrid vehicle 10 brakes or runs by inertia.
As described above, the hybrid vehicle 10 operates the engine clutch 14 to transmit power or separate power between the motor 12 and the engine 11 for switching the mode and the like. Operation hydraulic pressure of the engine clutch that determines an operation of the engine clutch 14 influences drivability, power performance, and fuel efficiency of the hybrid vehicle, thus, the operation hydraulic pressure of the engine clutch needs to be controlled accurately.
However, operation variations of the engine clutch, as illustrated in FIG. 3, may be generated according to characteristics and operating environments of the engine clutch. The operation variations may include an offset variation associated with torque transmission start hydraulic pressure, a gain variation associated with transmission torque, and a linearity variation.
Each variation described above may be generated by characteristics of the engine clutch, the solenoid valve, and the like. Further, the each variation may be generated based on a difference between respective components of the engine clutch, for example, component assembling tolerance, characteristic deviation of current-versus-pressure of the solenoid valve, and characteristic deviation according to passage of a usage period. When the each variation is not corrected through learning, it may negatively influence drivability, power performance, and fuel efficiency of the hybrid vehicle.
In a method of correcting each variation through learning according to the related art, accuracy of learning may be low and time of learning may be long since only a hydraulic pressure sensor or a motor is used. In other words, when learning is performed using only the hydraulic pressure sensor, accuracy of the learning may be low due to the offset variation and gain variation of the hydraulic pressure sensor, and mechanical deviation of the engine clutch and the solenoid valve generated after applying the pressure. Further, when learning is performed using only the motor, time of the learning may be long since learning is individually performed at each applied pressure to correct linearity variation.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.